Negative-pressure treatment with area stabilization

ABSTRACT

An apparatus for applying negative pressure to a tissue site proximate a patient&#39;s foot may include a tissue interface, a sole, a toe box, a cover, and an interface. The tissue interface may be configured to be circumferentially disposed around the tissue site. The sole may be configured to support the tissue interface. The toe box may be coupled to the sole. The cover may be configured to be coupled to the leg and to the sole to cover the tissue interface. The cover and the sole may form a chamber containing the tissue interface and may seal the tissue interface within the chamber. The interface may be configured to fluidly couple the tissue interface to a source of negative pressure, which can be delivered to the tissue interface for distribution to the tissue site.

RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. § 119(e), of the filing of U.S. Provisional Patent Application Ser. No. 62/826,050 entitled “NEGATIVE-PRESSURE TREATMENT WITH AREA STABILIZATION,” filed Mar. 29, 2019, which is incorporated herein by reference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to dressings for tissue treatment with negative pressure and methods of using the dressings for tissue treatment with negative pressure.

BACKGROUND

Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of the wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as “negative-pressure therapy,” but is also known by other names, including “negative-pressure wound therapy,” “reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,” and “topical negative-pressure,” for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times.

Additionally, the application of negative therapy may be beneficial for the healing of sprains or strains at tissue sites where there may be no open wound.

While the clinical benefits of negative-pressure therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for treating tissue in a negative-pressure therapy environment are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter.

For example, in some embodiments, an apparatus for applying negative pressure to a tissue site proximate a foot of a patient may include a boot having a sole and a toe box coupled to the sole. The boot may be adapted to receive the foot of a patient, wherein a tissue interface can be placed around a portion of the foot, the ankle, and a portion of the leg. The tissue interface may be configured to not cover the toes. The boot may further include one or more stabilizing members, such as for example rigid stays, that extend upward from the sole to provide stability to the ankle joint. The apparatus may further include a cover that may be sealed to the leg above the tissue interface by a first sealing member and may be sealed at a connection point around the perimeter of the sole by a second sealing member. The toe box may be formed of a rigid material that prevents the toes from being compressed under negative pressure.

More generally, in some embodiments, an apparatus for applying negative pressure to a tissue site proximate a patient's foot may include a tissue interface, a sole, a toe box, a cover, and an interface. The tissue interface may be configured to be circumferentially disposed around the tissue site. The sole may be configured to support the tissue interface. The toe box may be coupled to the sole. The cover may be configured to be coupled to the leg and to the sole to cover the tissue interface. The cover and the sole may form a chamber containing the tissue interface and may seal the tissue interface within the chamber. The interface may be configured to fluidly couple the tissue interface to a source of negative pressure, which can be delivered to the tissue interface for distribution to the tissue site.

In some embodiments, the cover may have a first end configured to be sealed to the leg by a first sealing member and a second end configured to be sealed to the sole by a second sealing member.

In some embodiments, the tissue interface may be configured to circumferentially cover a portion of the leg, the ankle, and the foot of the patient. For example, the tissue interface may be a sleeve or may have a boot shape. In some embodiments, the tissue interface may not be configured to cover the toes of the patient. In some embodiments, the tissue interface may be configured to cause the cover to collapse upon application of negative pressure, stiffening the cover to stabilize the tissue site and pulling the tissue site radially outward.

In some embodiments, the toe box may be configured to prevent the toes of the patient from being compressed when negative pressure is applied to the tissue interface.

Some example embodiments may include an apparatus for applying negative pressure to a tissue site proximate a foot of a patient. The apparatus may have a tissue interface, a boot having a toe box, a cover, and an interface. The tissue interface may be configured to be circumferentially disposed around the tissue site. The boot may be configured to support the tissue interface. The cover may be configured to be coupled to the leg and to the boot to cover the tissue interface. The cover and the boot may form a chamber containing the tissue interface and may seal the tissue interface within the chamber. The interface may be configured to fluidly couple the tissue interface to a source of negative pressure, which can be delivered to the tissue interface for distribution to the tissue site.

In some embodiments, a system for applying negative pressure to a tissue site proximate a foot of a patient may include a negative-pressure source, a tissue interface, a sole, a toe box, and a cover. The tissue interface may be configured to be circumferentially disposed around the tissue site. The sole may be configured to support the tissue interface. The toe box may be coupled to the sole. The cover may be configured to be coupled to the leg and the sole to cover the tissue interface. The cover and the sole may form a sealed chamber containing the tissue interface. The negative-pressure source can be configured to be fluidly coupled with the tissue interface.

In some embodiments, a system for applying negative pressure to a tissue site proximate a foot of a patient may include a negative-pressure source, a tissue interface, a boot, and a cover. The tissue interface may be configured to be circumferentially disposed around the tissue site, and the boot may be configured to receive the tissue interface. The boot may have a toe box in some embodiments, which can be configured to protect the toes from compression under negative pressure. The cover can be configured to be coupled to the leg and to the boot to cover the tissue interface. The cover and the boot can form a chamber containing the tissue interface, and the negative-pressure source can be configured to be fluidly coupled to the tissue interface through the cover.

In yet other example embodiments, a method for applying negative pressure to a foot may include disposing circumferentially a tissue interface around a tissue site proximate the foot, enclosing the tissue interface with a cover, sealing the cover around the leg of the patient above the tissue interface, inserting the tissue interface into a sole, inserting the toes of the patient into a toe box coupled to the sole, sealing the cover to the sole, fluidly coupling the tissue interface to a negative-pressure source, and applying a negative pressure to the tissue interface.

Objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example embodiment of a therapy system that can provide negative-pressure treatment and instillation treatment in accordance with this specification;

FIG. 2 is a side view of an example of a dressing, illustrating additional details that may be associated with some embodiments;

FIG. 3 is a cutaway view of the dressing of FIG. 2;

FIG. 4 and FIG. 5 are isometric views of an example of a tissue interface, illustrating additional details that may be associated with some dressings;

FIG. 6 is a cutaway view of another example of a dressing, illustrating additional details that may be associated with some embodiments; and

FIG. 7 is a section view of FIG. 3.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but it may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription.

FIG. 1 is a simplified functional block diagram of an example embodiment of a therapy system 100 that can provide negative-pressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification.

The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including, but not limited to, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted.

The therapy system 100 may include a source or supply of negative pressure, such as a negative-pressure source 105, and one or more distribution components. A distribution component is preferably detachable and may be disposable, reusable, or recyclable. A dressing, such as a dressing 110, and a fluid container, such as a container 115, are examples of distribution components that may be associated with some examples of the therapy system 100. As illustrated in the example of FIG. 1, the dressing 110 may comprise or consist essentially of a tissue interface 120, a cover 125, or both in some embodiments.

A fluid conductor is another illustrative example of a distribution component. A “fluid conductor,” in this context, broadly includes a tube, pipe, hose, conduit, or other structure with one or more lumina or open pathways adapted to convey a fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. Moreover, some fluid conductors may be molded into or otherwise integrally combined with other components. Distribution components may also include or comprise interfaces or fluid ports to facilitate coupling and de-coupling other components. In some embodiments, for example, a dressing interface may facilitate coupling a fluid conductor to the dressing 110. For example, such a dressing interface may be a SENSAT.R.A.C.™ Pad available from Kinetic Concepts, Inc. of San Antonio, Tex.

The therapy system 100 may also include a regulator or controller, such as a controller 130. Additionally, the therapy system 100 may include sensors to measure operating parameters and provide feedback signals to the controller 130 indicative of the operating parameters. As illustrated in FIG. 1, for example, the therapy system 100 may include a first sensor 135 and a second sensor 140 coupled to the controller 130.

Some components of the therapy system 100 may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate therapy. For example, in some embodiments, the negative-pressure source 105 may be combined with the controller 130 and other components into a therapy unit.

In general, components of the therapy system 100 may be coupled directly or indirectly. For example, the negative-pressure source 105 may be directly coupled to the container 115 and may be indirectly coupled to the dressing 110 through the container 115. Coupling may include fluid, mechanical, thermal, electrical, or chemical coupling (such as a chemical bond), or some combination of coupling in some contexts. For example, the negative-pressure source 105 may be electrically coupled to the controller 130 and may be fluidly coupled to one or more distribution components to provide a fluid path to a tissue site. In some embodiments, components may also be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material.

A negative-pressure supply, such as the negative-pressure source 105, may be a reservoir of air at a negative pressure or may be a manual or electrically-powered device, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. “Negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment. In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. References to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure. While the amount and nature of negative pressure provided by the negative-pressure source 105 may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges are between −50 mm Hg (−6.7 kPa) and −300 mm Hg (−39.9 kPa).

The container 115 is representative of a container, canister, pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluids. In other environments, fluids may be properly disposed of without rigid container storage, and a re-usable container could reduce waste and costs associated with negative-pressure therapy.

A controller, such as the controller 130, may be a microprocessor or computer programmed to operate one or more components of the therapy system 100, such as the negative-pressure source 105. In some embodiments, for example, the controller 130 may be a microcontroller, which generally comprises an integrated circuit containing a processor core and a memory programmed to directly or indirectly control one or more operating parameters of the therapy system 100. Operating parameters may include the power applied to the negative-pressure source 105, the pressure generated by the negative-pressure source 105, or the pressure distributed to the tissue interface 120, for example. The controller 130 is also preferably configured to receive one or more input signals, such as a feedback signal, and programmed to modify one or more operating parameters based on the input signals.

Sensors, such as the first sensor 135 and the second sensor 140, are generally known in the art as any apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the first sensor 135 and the second sensor 140 may be configured to measure one or more operating parameters of the therapy system 100. In some embodiments, the first sensor 135 may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. In some embodiments, for example, the first sensor 135 may be a piezo-resistive strain gauge. The second sensor 140 may optionally measure operating parameters of the negative-pressure source 105, such as a voltage or current, in some embodiments. Preferably, the signals from the first sensor 135 and the second sensor 140 are suitable as an input signal to the controller 130, but some signal conditioning may be appropriate in some embodiments. For example, the signal may need to be filtered or amplified before it can be processed by the controller 130. Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal.

The tissue interface 120 can be generally adapted to partially or fully contact a tissue site. The tissue interface 120 may take many forms, and may have many sizes, shapes, or thicknesses, depending on a variety of factors, such as the type of treatment being implemented or the nature and size of a tissue site. For example, the size and shape of the tissue interface 120 may be adapted to the contours of deep and irregular shaped tissue sites. Any or all of the surfaces of the tissue interface 120 may have an uneven, coarse, or jagged profile.

In some embodiments, the tissue interface 120 may comprise or consist essentially of a manifold. A manifold in this context may comprise or consist essentially of a means for collecting or distributing fluid across the tissue interface 120 under pressure. For example, a manifold may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across the tissue interface 120, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source.

In some illustrative embodiments, a manifold may comprise a plurality of pathways, which can be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, a manifold may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that can be adapted to form interconnected fluid pathways (e.g., channels) may include cellular foam, including open-cell foam such as reticulated foam; porous tissue collections; and other porous material such as gauze or felted mat that generally include pores, edges, and/or walls. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, a manifold may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, a manifold may be molded to provide surface projections that define interconnected fluid pathways.

In some embodiments, the tissue interface 120 may comprise or consist essentially of reticulated foam having pore sizes and free volume that may vary according to needs of a prescribed therapy. For example, reticulated foam having a free volume of at least 90% may be suitable for many therapy applications, and foam having an average pore size in a range of 400-600 microns (40-50 pores per inch) may be particularly suitable for some types of therapy. The tensile strength of the tissue interface 120 may also vary according to needs of a prescribed therapy. For example, the tensile strength of foam may be increased for instillation of topical treatment solutions. The 25% compression load deflection of the tissue interface 120 may be at least 0.35 pounds per square inch, and the 65% compression load deflection may be at least 0.43 pounds per square inch. In some embodiments, the tensile strength of the tissue interface 120 may be at least 10 pounds per square inch. The tissue interface 120 may have a tear strength of at least 2.5 pounds per inch. In some embodiments, the tissue interface 120 may be foam comprised of polyols such as polyester or polyether, isocyanate such as toluene diisocyanate, and polymerization modifiers such as amines and tin compounds. In some examples, the tissue interface 120 may be reticulated polyurethane foam such as found in GRANUFOAM™ dressing or V.A.C. VERAFLO™ dressing, both available from Kinetic Concepts, Inc. of San Antonio, Tex.

The thickness of the tissue interface 120 may also vary according to needs of a prescribed therapy. For example, the thickness of the tissue interface may be decreased to reduce tension on peripheral tissue. The thickness of the tissue interface 120 can also affect the conformability of the tissue interface 120. In some embodiments, a thickness in a range of about 5 millimeters to about 30 millimeters may be suitable.

The tissue interface 120 may be either hydrophobic or hydrophilic. In an example in which the tissue interface 120 may be hydrophilic, the tissue interface 120 may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site. The wicking properties of the tissue interface 120 may draw fluid away from a tissue site by capillary flow or other wicking mechanisms. An example of a hydrophilic material that may be suitable is a polyvinyl alcohol, open-cell foam such as V.A.C. WHITEFOAM™ dressing available from Kinetic Concepts, Inc. of San Antonio, Tex. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity.

In some embodiments, the tissue interface 120 may be constructed from bioresorbable materials. Suitable bioresorbable materials may include, without limitation, a polymeric blend of polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blend may also include, without limitation, polycarbonates, polyfumarates, and capralactones. The tissue interface 120 may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the tissue interface 120 to promote cell-growth. A scaffold is generally a substance or structure used to enhance or promote the growth of cells or formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials.

In some embodiments, the cover 125 may provide a bacterial barrier and protection from physical trauma. The cover 125 may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover 125 may comprise or consist of, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover 125 may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least 250 grams per square meter per twenty-four hours (g/m²/24 hours) in some embodiments, measured using an upright cup technique according to ASTM E96/E96M Upright Cup Method at 38° C. and 10% relative humidity (RH). In some embodiments, an MVTR up to 5,000 g/m²/24 hours may provide effective breathability and mechanical properties.

In some example embodiments, the cover 125 may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of about 25 to about 50 microns. In some embodiments, the cover 125 may have a thickness greater than 50 microns. In some embodiments, the cover may have a thickness in the range of about 50 microns to about 3.175 millimeters. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained. The cover 125 may comprise, for example, one or more of the following materials: polyurethane (PU), such as hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; silicones, such as hydrophilic silicone elastomers; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; ethylene vinyl acetate (EVA); co-polyester; and polyether block polymide copolymers. Such materials are commercially available as, for example, Tegaderm® drape, commercially available from 3M Company, Minneapolis, Minn.; polyurethane (PU) drape, commercially available from Avery Dennison Corporation, Pasadena, Calif.; polyether block polyamide copolymer (PEBAX), for example, from Arkema S.A., Colombes, France; and Inspire 2301 and Inpsire 2327 polyurethane films, commercially available from Expopack Advanced Coatings, Wrexham, United Kingdom. In some embodiments, the cover 125 may comprise INSPIRE 2301 having an MVTR (upright cup technique) of 2600 g/m²/24 hours and a thickness of about 30 microns. In some embodiments, the cover 125 may comprise a non-porous film.

An attachment device may be used to attach the cover 125 to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover 125 to epidermis around a tissue site. In some embodiments, for example, some or all of the cover 125 may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight of about 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel.

In operation, the tissue interface 120 may be placed within, over, on, or otherwise proximate to a tissue site. If the tissue site is a wound, for example, the tissue interface 120 may partially or completely fill the wound, or it may be placed over the wound. The cover 125 may be placed over the tissue interface 120 and sealed to an attachment surface near a tissue site. For example, the cover 125 may be sealed to undamaged epidermis peripheral to a tissue site. Thus, the dressing 110 can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the negative-pressure source 105 can reduce pressure in the sealed therapeutic environment.

The fluid mechanics of using a negative-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to negative-pressure therapy are generally well-known to those skilled in the art, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” negative pressure, for example.

In general, exudate and other fluid flow toward lower pressure along a fluid path. Thus, the term “downstream” typically implies something in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term “upstream” implies something relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications, such as by substituting a positive-pressure source for a negative-pressure source, and this descriptive convention should not be construed as a limiting convention.

With tissue sites having open wounds, negative pressure applied across the tissue site through the tissue interface 120 in the sealed therapeutic environment can induce macro-strain and micro-strain in the tissue site. Negative pressure can also remove exudate and other fluid from a tissue site, which can be collected in container 115.

In some embodiments, the controller 130 may receive and process data from one or more sensors, such as the first sensor 135. The controller 130 may also control the operation of one or more components of the therapy system 100 to manage the pressure delivered to the tissue interface 120. In some embodiments, the controller 130 may include an input for receiving a desired target pressure and may be programmed for processing data relating to the setting and inputting of the target pressure to be applied to the tissue interface 120. In some example embodiments, the target pressure may be a fixed pressure value set by an operator as the target negative pressure desired for therapy at a tissue site and then provided as input to the controller 130. The target pressure may vary from tissue site to tissue site based on the type of tissue forming a tissue site, the type of injury or wound (if any), the medical condition of the patient, and the preference of the attending physician. After selecting a desired target pressure, the controller 130 can operate the negative-pressure source 105 in one or more control modes based on the target pressure and may receive feedback from one or more sensors to maintain the target pressure at the tissue interface 120.

In some embodiments, the controller 130 may have a continuous pressure mode, in which the negative-pressure source 105 is operated to provide a constant target negative pressure for the duration of treatment or until manually deactivated. Additionally or alternatively, the controller may have an intermittent pressure mode. For example, the controller 130 can operate the negative-pressure source 105 to cycle between a target pressure and atmospheric pressure. For example, the target pressure may be set at a value of −135 mmHg for a specified period of time (e.g., 5 min), followed by a specified period of time (e.g., 2 min) of deactivation. The cycle can be repeated by activating the negative-pressure source 105 which can form a square wave pattern between the target pressure and atmospheric pressure.

In some example embodiments, the increase in negative-pressure from ambient pressure to the target pressure may not be instantaneous. For example, the negative-pressure source 105 and the dressing 110 may have an initial rise time. The initial rise time may vary depending on the type of dressing and therapy equipment being used. For example, the initial rise time for one therapy system may be in a range of about 20-30 mmHg/second and in a range of about 5-10 mmHg/second for another therapy system. If the therapy system 100 is operating in an intermittent mode, the repeating rise time may be a value substantially equal to the initial rise time.

In some example dynamic pressure control modes, the target pressure can vary with time. For example, the target pressure may vary in the form of a triangular waveform, varying between a negative pressure of 50 and 135 mmHg with a rise time set at a rate of +25 mmHg/min. and a descent time set at −25 mmHg/min. In some embodiments of the therapy system 100, the triangular waveform may vary between negative pressure of 25 and 135 mmHg with a rise time set at a rate of +30 mmHg/min and a descent time set at −30 mmHg/min.

In some embodiments, the controller 130 may control or determine a variable target pressure in a dynamic pressure mode, and the variable target pressure may vary between a maximum and minimum pressure value that may be set as an input prescribed by an operator as the range of desired negative pressure. The variable target pressure may also be processed and controlled by the controller 130, which can vary the target pressure according to a predetermined waveform, such as a triangular waveform, a sine waveform, or a saw-tooth waveform. In some embodiments, the waveform may be set by an operator as the predetermined or time-varying negative pressure desired for therapy.

In addition to providing negative-pressure therapy to a tissue site having an open wound, the therapy system 100 described herein may be used to treat tissue sites that have intact skin or epidermis but include sprains and strains to subcutaneous tissue such as, for example, a ligament or a muscle.

FIG. 2 is a side view of an example of the dressing 110, illustrating additional details that may be associated with some embodiments. In the example embodiment of FIG. 2, the dressing 110 is configured for delivering a negative pressure to a tissue site 200. As illustrated in the example of FIG. 2, the tissue site 200 may be on or proximate a foot 205 of a patient. The tissue interface 120 may be configured to be circumferentially disposed around the tissue site 200. Also included with the dressing 110 of FIG. 2 is a boot 210, which may comprise a sole 215, a toe box 220, and one or more optional stabilizing members 225. The boot 210 may be configured to support one or more of the foot 205, an ankle 230, and a portion of a leg 235. The cover 125 may be sealed to the leg 235 superior to the ankle 230 by a first sealing member 240 and to a perimeter 250 of the sole 215 by a second sealing member 245. The dressing 110 may further include a dressing interface 255, which can fluidly couple the tissue interface 120 to the negative-pressure source 105 via a fluid conductor 260 to deliver negative pressure to the tissue site 200.

FIG. 3 is a cutaway view of the dressing 110 of FIG. 2. As shown, in some embodiments, the tissue interface 120 comprises a primary manifold 300 that conforms to the shape of a portion of the leg 235, the ankle 230, and the foot 205. The tissue interface 120 may have two open ends and may not cover the toes 302 of the patient. In some embodiments, the tissue interface 120 may be formed in the shape of an open-toed sock or a sleeve, which may be pulled over the tissue site 200.

In some embodiments, the tissue interface 120 may be molded as a single component in a generally tubular shape having a first end 305 and a second end 310 that are open, and the tissue interface 120 may be configured to be pulled over the foot 205. The toes 302 may be inserted into the tissue interface 120 through the first end 305. The tissue interface 120 may be pulled up the foot 205 such that the first end 305 extends over and past the ankle 230 and up at least a portion of the leg 235. The toes 302 of the foot 205 can extend out and beyond the second end 310 of the tissue interface 120. In some embodiments, the tissue interface 120 may be boot shaped. For example, the tissue interface 120 may have a sole portion 315, a vamp portion 320 coupled to the sole portion 315, a quarter portion 325 coupled to the sole portion 315 and the vamp portion 320, and a calf portion 330 coupled to and extending away from the quarter portion 325. In some embodiments, the tissue interface 120 may comprise a sheet or tape of open-cell foam, which can be configured to be wrapped around and circumferentially cover a portion of the leg 235, the ankle 230, and the foot 205.

The tissue interface 120 may take many forms and may come in many sizes, shapes, or thicknesses depending on a variety of factors, such as the type of treatment being provided or the nature and size of the epidermis 335 at the tissue site 200. For example, the size and shape of the tissue interface 120 may be adapted to the contours of the extremities located at a joint, such as the ankle 230. The second open end 310 of the tissue interface 120 may abut or contact the open end of the toe box 220, leaving no gap between the tissue interface 120 and the toe box 220, which may reduce or eliminate the possibility of the epidermis 335 from being pulled up and pinched between the tissue interface 120 and the toe box 220. In some embodiments, there may be a gap between the tissue interface 120 and the toe box 220 such that the second open end 310 of the tissue interface 120 does not abut or contact the toe box 220.

Additionally, in some embodiments, the tissue interface 120 may comprise a comfort layer 340, which may be positioned between the primary manifold 300 and the tissue site 200. The comfort layer 340 may be employed to provide additional comfort for the patient rather than disposing the primary manifold 300 in direct contact with the epidermis 335. The comfort layer 340 may be any material that helps prevent skin irritation without significantly impeding airflow between the tissue interface 120 and the epidermis 335. The comfort layer 340 may also be any material that wicks liquids such as sweat away from the epidermis 335 to prevent maceration. In some examples, the comfort layer 340 may be a woven material or a polyester knit textile substrate. In some embodiments, the comfort layer 340 may be a stretchable knit sock. A textile known as InterDry™ available from Milliken Chemical located in Spartanburg, S.C., may be a suitable material for some embodiments of the comfort layer 340. The comfort layer 340 may also include antimicrobial substances or lubricants. In some embodiments, instead of a separate layer, the comfort layer 340 may be coupled, for example by a heat bond or any other technique, to the primary manifold 300, or may be an integral component of the primary manifold 300.

The boot 210 in the example of FIG. 3 is configured to support the tissue interface 120. Following application of the tissue interface 120 on the leg 235, the ankle 230, and the foot 205 of the patient, the foot 205 may be placed into the boot 210. The toes 302 of the patient may be received in the toe box 220 of the boot 210 and the sole of the patient may be supported by the sole 215 of the boot 210. The boot 210 may provide support and/or immobilize the tissue site 200 if appropriate or necessary. The toe box 220 may be sufficiently rigid to prevent collapse and support the cover 125 if subjected to negative pressure from the negative-pressure source 105. The toe box 220 may be configured to prevent the toes 302 of the patient from being compressed by the cover 125 if negative pressure is supplied to the tissue interface 120. In some embodiments, the toe box 220 may be formed from a closed-cell foam. The use of closed-cell foam for the toe box 220 may also allow for the transition from the toe box 220 to the tissue interface 120 to be minimized, which may reduce or eliminate the chance for blister formation. Additionally, in some embodiments, the toe box 220 may have a thickness that is equal or substantially equal to a thickness of the tissue interface 120. In some embodiments, the toe box 220 may comprise a rigid plastic or composite material. As shown in the example FIG. 3, the toe box 220 may be integrally formed with the sole 215. In some embodiments, the toe box 220 may be separately manufactured and permanently or releasably coupled to the sole 215. In some embodiments, the toe box 220 may be clear or transparent to permit a patient or a physician to view the toes 302 of the patient through the toe box 220 to check for blood flow or circulation through the toes 302. In some embodiments, the toe box 220 may be colored (e.g., skin colored).

Additionally, in some embodiments, the boot 210 may further include one or more stabilizing members 225, which can extend away from the sole 215 along and proximate the calf portion 330 of the tissue interface 120. In some examples, a first stabilizing member 225 may extend from a medial side of the sole 215 and a second stabilizing member (not shown) may extend from a lateral side of the sole 215. The first stabilizing member 225 and the second stabilizing member may be generally aligned with the ankle 230 and the fibula and/or tibia of the patient. The first stabilizing member 225 and the second stabilizing member may stabilize the tissue interface 120 and/or the ankle 230 of the patient. The sole 215 and the first stabilizing member 225 and the second stabilizing member, if included, may be sufficiently rigid to protect the tissue interface 120 from being compressed by contact from the external environment that collapses the tissue interface 120, preventing the tissue interface 120 from distributing negative pressure to the tissue site 200.

As illustrated in the example of FIG. 3, the cover 125 may have a tubular or sleeve shape and may have a first end 345 and a second end 350 that are open. The first end 345 of the cover 125 may be sealed to the leg 235 of the patient superior to the tissue interface 120 by the first sealing member 240, which can extend around the leg 235. The second end 350 may be sealed to the sole 215 of the boot 210 by the second sealing member 245, which can extend around the sole 215. In some examples, the second end 350 may have a larger diameter than the diameter of the first end 345. The cover 125 of FIG. 3 is configured to fit over the tissue interface 120 and the sole 215. The cover 125 and the sole 215 can cooperate to form a chamber 355 containing the tissue interface 120 and to seal the tissue interface 120 within the chamber 355. The cover 125 may comprise a sealing material that can provide a fluid seal between two environments or components, such as, for example, between a therapeutic environment adjacent the tissue site 200 and a local external environment surrounding the cover 125. In some embodiments, the cover 125 may be configured to be wrapped around and circumferentially cover the tissue interface 120 and at least a portion of the boot 210. The cover 125 may also extend circumferentially around the tissue site 200, and in cooperation with the sole 215, the first sealing member 240, and the second sealing member 245, can form the chamber 355 enclosing the tissue site 200 to provide a negative-pressure environment. A negative pressure from the negative-pressure source 105 may be distributed to the tissue site 200 by the tissue interface 120. The sealing material forming the cover 125 may be, for example, an impermeable or semi-permeable material that provides a seal adequate to maintain a desired negative pressure within the chamber 355. In some embodiments, the cover 125 may be molded as a single component in a generally tubular shape formed from the sealing material that is stretched over the foot 205 and at least a portion of the leg 235. The cover 125 may fit over the tissue interface 120 and the sole 215 of the boot 210. The cover 125 may have a thickness in a range of about 25 to about 50 microns. However, the cover 125 may have a thickness greater than 50 microns. In some embodiments, the cover 125 may have a thickness in the range of about 25 microns to about 3.175 millimeters.

The first sealing member 240 and the second sealing member 245 are examples of attachment devices, which can be configured to seal the cover 125 to the patient and the sole 215, respectively. For example, the first sealing member 240 may be an elastic tape wrapped around the first end 345 of the cover 125 against the epidermis 335 to provide a fluid seal at the first end 345 of the cover 125. In some embodiments, the first sealing member 240 may be disposed between the cover 125 and the epidermis 335 for attaching the cover 125 to an attachment surface, such as the epidermis 335, a gasket, or another sealing member. The first sealing member 240 may also be an adhesive material configured to prevent the cover 125 from slipping down the leg 235. For example, the first sealing member 240 may be a silicone tape or adhesive gasket. The first sealing member 240 may take many forms that can provide both sealing and adhesive qualities without irritating or macerating the epidermis 335. The first sealing member 240 may be a medically-acceptable, pressure-sensitive adhesive that extends around the periphery of the first end 345 of the cover 125 to provide an airtight seal between the epidermis 335 and the cover 125. Other exemplary embodiments of the first sealing member 240 may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, organogel, or an acrylic adhesive. In some embodiments, the first sealing member 240 may be non-adhesive. For example, the first sealing member 240 may comprise a neoprene sleeve that can be secured on the leg 235 and over the cover 125 to provide a fluid seal. In some embodiments, the first sealing member 240 may comprise a silicone gasket or ring seal having a central aperture through which the patient may insert their leg 235. For example, such a ring seal may be a diaphragm from the SEAL-TIGHT cast and bandage protector available from Brownmed of Boston, Mass.

The second sealing member 245 may also be an elastic tape in some embodiments. For example, the second sealing member 245 may be an elastic tape that can be wrapped around the second end 350 of the cover 125 against the sole 215 to provide a fluid seal at the second end 350 of the cover 125. The second end 350 of the cover 125 may be placed at or over the perimeter 250 of the sole 215. The second sealing member 245 may be wrapped around the perimeter 250 of the sole 215 and the second end 350 of the cover 125 to seal the cover 125. In some embodiments, the second sealing member 245 may be disposed between the cover 125 and the sole 215 for attaching the cover 125 to an attachment surface such as, for example, a gasket, another sealing member, or the sole 215. The second sealing member 245 may also be an adhesive material that prevents the cover 125 from slipping up from the sole 215. The second sealing member 245 may take many forms that can provide both sealing and adhesive qualities. In some embodiments, the second sealing member 245 may be the same as the first sealing member 240. For example, the second sealing member 245 may also be a medically-acceptable, pressure-sensitive adhesive that extends around the periphery of the second end 350 of the cover 125 to provide an airtight seal between the sole 215 and the cover 125. Other exemplary embodiments of the second sealing member 245 may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, organogel, or an acrylic adhesive. Although the second end 350 of the cover 125 is shown in FIG. 3 as extending around the perimeter 250 of the sole 215, in some embodiments the second end 350 of the cover 125 may extend partially around the perimeter 250 of the sole 215 and then may extend over the toe box 220. The second sealing member 245 may follow a similar path or shape to fluidly seal the cover 125 to the boot 210. In some embodiments, for example, the second end 350 of the cover 125 may be sealed to another portion of the boot 210.

A negative pressure may be supplied to the chamber 355 via a fluid conductor 260 and a dressing interface 255. The fluid conductor 260 may be a flexible tube, for example, that can be fluidly coupled on one end to the dressing interface 255. The dressing interface 255 may be an elbow connector, as shown in the example of FIG. 3, which can be placed over an aperture 360 in the cover 125 to provide a fluid path between the fluid conductor 260 and the tissue interface 120.

Because the dressing 110 may be positioned on the epidermis 335 for a prolonged period of time, the tissue interface 120 may possess an antimicrobial property to mitigate the risk of fungal infection and the spread of such infections caused by perspiration and warm temperatures in the chamber 355. The antimicrobial property of the tissue interface 120 may reduce the effect of VOCs to reduce odors being generated by the dressing 110. The antimicrobial property may be achieved by means of a silver coating that covers the tissue interface 120 or by a silver additive to the cover 125. Using a tissue interface 120 having an antimicrobial property may be used in conjunction with a charcoal filter (not shown) in connection with providing a negative pressure to the dressing 110 via the fluid conductor 260 to further reduce odors generated by the dressing 110.

FIG. 4 and FIG. 5 are isometric views of an example embodiment of the tissue interface 120 that may be associated with some dressings 110. As shown in the example of FIG. 4, the tissue interface 120 may be formed of a sheet of material that may be placed against the patient and may be wrapped around at least a portion of the foot 205, the ankle 230, and the leg 235. The tissue interface 120 may have an anatomical shape in some embodiments, or may be shaped such that when wrapped around the patient it is anatomically shaped or conforms to an anatomical shape. For example, in FIG. 5 the tissue interface 120 has a shape configured to conform to at least a portion of the foot 205, the ankle 230, and the leg 235. Additionally shown in the example of FIG. 5, the tissue interface 120 may form a seam 500 where the tissue interface 120 abuts against itself when wrapped around the patient. Although a single seam 500 is illustrated in the example of FIG. 5, the tissue interface 120 may form multiple seams when wrapped around the patient. Additionally, although the seam 500 is illustrated as extending generally in a line down the front of the leg 235 and the foot 205, the one or more seams 500 may be non-linear and may be located along other portions of the leg 235 and foot 205 of the patient. As further illustrated in the example of FIG. 5, one or more straps 505 may be coupled to the tissue interface 120 over the seams 500 to close the seams 500 and to ensure that the seams 500 remain closed when the dressing 110 is in use. The straps 505 may prevent the seams 500 from opening or spreading apart if a negative pressure is applied to the tissue interface 120. In some embodiments, the straps 505 may couple to the tissue interface 120 via an adhesive (e.g., a pressure-sensitive adhesive), a hook-and-loop style fastener (e.g., VELCRO fastener), or any other suitable coupling mechanism. In some embodiments, as shown in the example of FIG. 5, the straps 505 may be short and may only extend around a portion of the tissue interface 120. In some embodiments, at least one of the straps 505 may extend circumferentially around the tissue interface 120 and couple with itself. In some embodiments, the straps 505 may comprise an elastic loop, which can be stretched and slid up the tissue interface 120 and if released, can hold the tissue interface 120 in place by the tension in the strap 505. As shown in FIG. 5, the tissue interface 120 may not cover the toes 302 of the patient. The tissue interface 120 shown in FIG. 5 may be particularly beneficial for patients whose injury to the tissue site is severe enough such that the patient is unable to insert their foot 205 into and through a tubular shaped tissue interface 120.

FIG. 6 is a cutaway view of another example of the dressing 110, illustrating additional details that may be associated with some embodiments. In the example embodiment of FIG. 6, the negative-pressure source 105 is contained within the boot 210. In some embodiments, the negative-pressure source 105 may be a compressible bladder system located in the sole 215 of the boot 210 that is operable by the patient. For example, the negative-pressure source 105 may comprise two or more compressible bladders 605. Each compressible bladder 605 may include a chamber wall 610 that substantially encloses a chamber 615. The compressible bladders 605 are movable between a compressed position and an expanded position to generate negative pressure. A resilient member 620, such as an open-cell foam, can be disposed within the chamber 615 to bias the compressible bladder 605 toward the expanded position.

In operation the compressible bladders 605 of FIG. 6 are positioned beneath the foot 205 of a patient. One of the compressible bladders 605 may be positioned under a heel region of the foot 205, and another of the compressible bladders 605 may be preferably positioned under a forefoot region of the foot 205. As the weight of the patient is exerted on a particular compressible bladder 605, the compressible bladder 605 is compressed to the compressed position and gas (e.g. air) that is within the chamber 615 is ejected through an outlet (not shown) and an outlet valve (not shown). As the weight of the patient is lifted from the compressible bladder 605 that has been compressed, the compressible bladder 605 begins to move toward the expanded position. The movement of the compressible bladder 605 toward the expanded position may be aided by the biasing member 620. As the compressible bladder 605 expands, a volume of the chamber 615 increases, which creates a negative pressure within the chamber 615. This negative pressure within the chamber 615 pulls fluid into the chamber 615 through an inlet valve (not shown) and the inlet 625. The reduced pressure generated by the compressible bladder 605 during expansion may be transmitted to the tissue interface 120 by the fluid conductors 630, which are fluidly coupled to the chamber 615 and the inlets 625 of each of the compressible bladders 605. As shown in example FIG. 6, the fluid conductors 630 may be located within the boot 210 and may have an inlet 635 located in the boot 210 within the chamber 615. If the inlets 635 of the fluid conductors 630 are located within the chamber 615, the fluid conductors 630 do not need to be mechanically coupled to the cover 125 in order to provide negative pressure to the tissue interface 120. The compressible bladder system may eliminate the need to include the dressing interface 255 or the aperture 360 in the cover 125. Additionally, by including the compressible bladder system in the boot 210, the need for an external negative-pressure source may be eliminated.

A method of treating the tissue site 200 with negative pressure may be carried out utilizing the dressing 110. Some embodiments of the dressing 110 may be configured for treating a foot. Other exemplary embodiments of the dressing 110 may be suitable for the treatment of ligaments or muscles associated with other joints such as, for example, a knee, ankle, wrist, or elbow joint. The method may comprise disposing circumferentially the tissue interface 120 around the tissue site. The method may further include enclosing the tissue interface 120 with the cover 125. The cover 125 may then be sealed around the leg 235 superior to the tissue interface 120. A first sealing member 240 may be used to seal the cover 125 around the leg 235. In some embodiments, for example, where the first sealing member 240 comprises a silicone ring or gasket, the first sealing member 240 may be applied around the leg 235 of the patient above the tissue site 200 prior to disposing the tissue interface 120 on the patient. The method may then continue with inserting the tissue interface 120 into the sole 215 of the boot 210 and inserting the toes 302 of the patient into the toe box 220 coupled to the sole 215. The cover 125 may then be sealed to the sole 215. The second sealing member 245 may be used to seal the cover 125 to the sole 215. The method may further include fluidly coupling the tissue interface 120 to the negative-pressure source 105. In some embodiments, for example, a dressing interface 255 may fluidly couple the negative-pressure source 105 to the tissue interface 120. Negative pressure may then be applied to the tissue site 200 through the tissue interface 120 within the sealed space between the cover 125 and the tissue site 200. The application of negative pressure can cause the cover 125 to collapse and stiffen, which can stabilize the tissue site 200. The epidermis 335 can also be pulled radially outward by the negative pressure, which can promote perfusion at the tissue site 200.

Such modes of treatment may be particularly advantageous for sprains and other damage to soft tissue. For example, some embodiments of the dressing 110 may cover only intact skin over a portion of the tissue site 200 having a sprain, without being wrapped around a limb. For example, if a sprain is close to the epidermal tissue, such embodiments may be applied more locally to that portion of intact skin that is adjacent the sprain.

The tissue interface 120 may be disposed proximate the epidermis 335 that extends over or around the tissue site 200 so that the chamber 355 envelops the sprain injury at the tissue site 200. The cover 125 can cover the tissue interface 120 to seal or enclose the tissue interface 120 and the epidermis 335 of the tissue site 200 within the chamber 355. Consequently, the cover 125 can also extend over the epidermis 335 of the tissue site 200, essentially forming the chamber 355 and enclosing the tissue site 200 to provide a negative-pressure environment wherein the negative pressure is distributed to the intact skin by the tissue interface 120. The dressing 110 can provide a sealed therapeutic environment proximate to the epidermis 335 surrounding a tissue site 200 and substantially isolated from the external, ambient environment outside the cover 125. In FIG. 2, FIG. 3, and FIG. 4, the dressing 110 is shown without applying a negative pressure to the tissue interface 120. If negative pressure is applied to the chamber 355, the cover 125 may collapse until most of the air is removed from the chamber 355. The cover 125 can initially collapse against the epidermis 335 surrounding the tissue site 200 and provides a certain amount of stiffening that can function like a splint to stabilize the tissue site 200 and the joint itself. The negative-pressure source 105 can continue to evacuate most of the air from the chamber 355 so that the cover 125 is fully collapsed and the tissue interface 120 is compressed.

FIG. 7 is a section view of FIG. 3 along line 7-7. As illustrated in the example of FIG. 7, after the cover 125 is fully collapsed, the negative pressure begins to pull the intact skin radially outwardly as shown by arrows 700. The flow channels within the tissue interface 120 do not collapse under the negative pressure. Instead, the flow channels of the tissue interface 120 remain open to apply the negative pressure to the epidermis 335. The negative pressure being distributed to the epidermis 335 by the tissue interface 120 can promote perfusion by pneumatically pulling the epidermis 335 toward the cover 125 for a sustained period of time rather than compressing the tissue site 200. An initial collapsing of the cover 125 can provide a certain amount of splinting at the tissue site 200 followed by a sustained decompression cycle within the chamber 355 that can promote perfusion. Increasing the thickness of the cover 125 can also increase the rigidity of the cover 125, which can allow for additional or increased lift to be applied to the epidermis 335 upon negative pressure being supplied to the tissue interface 120. The epidermis 335 may be forced out radially to the inside of the cover 125. In some embodiments, for example, the thickness of the tissue interface 120 may be increased and thickness of the cover 125 may be decreased, which can cause similar radial movement of the epidermis 335. Additionally or alternatively, as shown in the example of FIG. 7, the dressing 110 may also promote healing of a wound or incision 705 at the tissue site 200.

The systems, apparatuses, and methods described herein may provide significant advantages. For example, use of the dressing 110 with negative pressure to treat wounds, strains, sprains, and other injuries to ankles and other joints can significantly reduce recovery time. The standard of care for strains and sprains for many decades has included rest, ice, compression and elevation. After a period of anywhere from 10 days to 24 weeks for minor injuries, patients commonly report a reduction in pain and return to motion. For major injuries, however, patients report a reduction in pain after one year, two years, and even more time. Even after these lengthy time periods, an equally significant number of patients still report pain and no return to motion.

Healing time for more traumatic sprains and strains with rest, ice, compression, and elevation can be much longer, typically ranging from 4 to 6 months. Even then, if the injury is still unstable after this time, surgery is often required to stabilize the joint. This prolonged healing time represents a significant loss of mobility, and delay in return to functional activity. Even for the majority of sprains and strains, the current standard of care also suffers from several practical drawbacks in addition to inadequate healing. Ice can only be applied for a limited time, as prolonged contact is either not practical because it melts or causes even more discomfort and pain because of the cold temperature being applied to the affected extremity. Compression with current devices, especially with elastic wraps, is either inadequate for applying a sufficient and consistent positive force (e.g., the wrap slips over time or is applied and re-applied incorrectly), or actually restricts blood flow and lymph flow.

The dressing 110 can apply the negative pressure to the epidermis 335, extending over or surrounding the tissue site 200, which can effectively splint and stabilize a joint, such as the ankle joint 230 of the foot 205. Negative pressure applied to the epidermis 335 can also pull the tissue site 200 outwardly toward the cover 125. This pulling force adjacent to the epidermis 335, coupled with the immobilization of the joint, can stimulate the blood flow (perfusion) and lymphatic flow at the tissue site 200, which can accelerate healing of the damaged ligament and/or muscle. Damaged tissue can be properly supplied and evacuated with blood flow and lymph flow, thereby promoting perfusion in the subcutaneous portions of the tissue site 200 and reducing edema to accelerate healing. In contrast, current treatments may only temporarily reduce inflammation by icing and may actually constrict blood flow and lymph flow by compression. Moreover, stabilizing elements such as the stabilizing members 225 can significantly reduce or eliminate the risk of further injury to the tissue site 200. Additionally, the toe box 220 can allow the toes 302 to remain uncompressed when negative pressure is applied to the tissue site 200. Compression of the toes 302 under negative pressure may be uncomfortable or painful for some patients. Thus, by preventing compression of the toes 302 during negative-pressure therapy, patient comfort and compliance may also be increased.

Thus, the therapy system 100 can provide the advantages of managing pain by reducing swelling and inflammation, increasing stability to the tissue site 200, eliminating compression of the toes 302 of the patient, and accelerating healing by increasing blood flow and lymph flow.

While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing 110 may be separated from other components for manufacture or sale. In other example configurations, the controller 130 may also be manufactured, configured, assembled, or sold independently of other components.

The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims. 

What is claimed is:
 1. An apparatus for applying negative pressure to a tissue site proximate a foot of a patient, the apparatus comprising: a tissue interface configured to be circumferentially disposed around the tissue site; a sole configured to support the tissue interface; a toe box coupled to the sole; a cover configured to be coupled to the leg of the patient and the sole to cover the tissue interface and wherein the cover is configured to cooperate with the sole to form a sealed chamber containing the tissue interface to seal the tissue interface within the chamber; and an interface fluidly coupled to the tissue interface to deliver negative pressure to the tissue interface for distribution to the tissue site.
 2. The apparatus of claim 1, further comprising a first sealing member configured to extend around the leg of the patient above the tissue interface, the first sealing member configured to seal the cover to the leg of the patient.
 3. The apparatus of claim 2, wherein the cover has a first end configured to be sealed by the first sealing member.
 4. The apparatus of claim 1, further comprising a second sealing member configured to seal the cover to the sole.
 5. The apparatus of claim 4, wherein the cover has a second end configured to be sealed by the second sealing member.
 6. The apparatus of claim 1, wherein the tissue interface is boot shaped.
 7. The apparatus of claim 6, wherein the boot shaped tissue interface is configured to circumferentially cover a portion of the leg, ankle, and foot of the patient.
 8. The apparatus of claim 1, wherein the tissue interface comprises a porous material having open cells.
 9. The apparatus of claim 1, wherein the tissue interface comprises foam having open cells.
 10. The apparatus of claim 1, wherein the tissue interface is a tube configured to be pulled over the foot.
 11. The apparatus of claim 10, wherein the tube has an open first end and an open second end.
 12. The apparatus of claim 1, wherein the tissue interface does not cover the toes of the patient.
 13. The apparatus of claim 1, further comprising a comfort layer configured to be disposed in the chamber between the tissue site and the tissue interface.
 14. The apparatus of claim 13, wherein the comfort layer comprises a stretchable knit sock.
 15. The apparatus of claim 1, wherein the toe box comprises foam having closed cells.
 16. The apparatus of claim 1, wherein the toe box is configured to prevent the toes of the patient from being compressed when negative pressure is applied to the tissue interface.
 17. The apparatus of claim 1, wherein the sole further comprises one or more stabilizing members extending upward from the sole, and wherein the one or more stabilizing members are configured to be within the chamber.
 18. The apparatus of claim 17, wherein the one or more stabilizing members are configured to stabilize the tissue interface.
 19. The apparatus of claim 17, wherein the one or more stabilizing members are configured to stabilize the ankle of the patient.
 20. The apparatus of claim 1, wherein the sole further comprises a medial stabilizing member and a lateral stabilizing member extending upward from the sole.
 21. The apparatus of claim 1, wherein the sole and the toe box are part of a boot and the cover is configured to cover at least a portion of the boot. 